JP2009-291069A discloses a linear motor that displaces a tubular yoke and a rod relative to each other in an axial direction by attracting a permanent magnet disposed on an outer peripheral surface of the rod using a moving magnetic field generated around a coil disposed on an inner peripheral surface of the yoke. FIG. 5 of JP2009-291069A shows a so-called ten-pole, twelve-slot linear motor in which the number of permanent magnets positioned in the yoke is ten and the number of slots formed in the yoke for disposing the coils is twelve.